There are known prior art decorative supports intended to be used on a wearable object, such as a watch or piece of jewellery, and having decorative elements, such as stones and especially precious stones.
For this reason, the support is generally made of metal alloy and is machined to form housings therein. The decorative elements may be mounted in these housings by pressing-in or by setting. In the case of assembly by setting, gripping means in the form of hooks are made during the machining operation. Generally speaking, these hooks are made with the material forming the wearable object, that is to say in one piece with the object. When a decorative element is required to be set, the latter is placed in a housing and the gripping means are cold worked and folded down so as to maintain said decorative element in the housing. This setting method is widely used for setting precious stones on metal supports since the metal has an advantageous capacity for plastic deformation. This capacity is even more advantageous with precious metals such as gold, since these precious metals are ductile and can easily be shaped.
Nevertheless, one drawback of this method is that it is limited to supports made of ductile metals or metal alloys. However, timepieces are increasingly made of materials with no plastic deformation, which are often hard and/or brittle, such as for example, ceramics, sapphire, silicon, composites (for example cermets) or even intermetallic alloys.
Consequently, it is no longer possible to use the current method for setting decorative elements, such as precious stones.
This setting operation can be replaced by an adhesive bonding operation. The drawback of adhesive bonding is that it cannot ensure 100% retention of the stones since, unlike setting, this technique does not involve mechanical retention of the stones. Indeed, as the bonded areas are in most cases exposed to the external environment (humidity, sweat, UV, air pollution, . . . ) this makes it difficult for the bond to hold in the long term. Consequently, the stones are not guaranteed to be held in place which is unacceptable for high quality products. There is also a risk of the adhesive salting-out products that are toxic and/or corrosive for the other components of the watch or piece of jewellery. Further, the decorative elements require prior machining, which may be difficult and expensive, particularly if the decorative elements have complicated geometries.
Another solution was proposed in EP Patent 2315673; this solution consists of inlaying a decorative element made of an amorphous material by pressing it into a support. This method requires the use of amorphous preforms. However, the number of alloys that exist in amorphous form is limited, so that it is not always possible to find an alloy having the required colour matching the watch or the piece of jewellery. For example, amorphous alloys with a yellow or red gold colour do not exist. Moreover, the inlaying method requires the application of a certain pressing force, so that it is difficult to utilise when the support is made of fragile or brittle material.
Another solution was proposed in EP Patent Application 2796297, consisting, in particular, in setting a decorative element in a substrate made of an amorphous alloy. However, the various methods describe heating and then cooling the amorphous metal which must necessarily be performed quickly to preserve the amorphous state of the metal. Rapid cooling creates a thermal shock which can cause internal stresses to appear in the support and thus lead to deformations or cracks. Further, the setting method necessarily involves deforming the gripping means, at the moment of setting, which may prove difficult when using an amorphous metal which might be difficult to deform due to its specific elastic properties. Moreover, as indicated above, the number of existing alloys in amorphous form is limited, so that it is not always possible to find an alloy having the desired colour matching the watch or piece of jewellery.